1. Field of the Invention
This present invention relates to a flying craft wherein the craft uses a computer-implemented control algorithm to maintain altitude control and stabilize the roll of the craft about two axes by using variations in output from fixed thrusters. Applications include, but are not restricted to, toys, hobby crafts, and crafts capable of transporting heavy or large loads.
2. Description of Prior Art
Searches were conducted in the following fields: 244/17.13; 244/76; and 244/23.
Alistair J. Jackson, U.S. Pat. No. 4,664,340, May 12, 1987, discloses a stabilization system for hovering and flying vehicles. The patent application included block diagrams which lay out in a non-specific manner the concept of using altitude controls and altitude sensors to measure the height and orientation of a hovering craft.
There are shortcomings in the control method outlined by Jackson.
First and foremost, the block diagram shown in FIG. 6 (Ref. Jackson FIG. 6) lays out the control method in only the broadest conceptual terms. It is not explained with enough specifity to enable an engineer or other practitioner familiar with the art to build it.
In order for a physically realizable feedback controller to function, among other requirements, it must apply actual numerical values of gain to the system error signals (Jackson calls these "difference signals"). The error signals are signals which represent the difference between operator commands and the current state of the craft. If indeed those feedback gains were known to Jackson, they are not specified in the patent. Because of this omission, the controller outlined could not be built as specified.
Another apparent shortcoming of Jackson's control method is that there is no formal method outlined for integrating the altitude error and the roll error to bring about the coordinated movements of the craft to simultaneously, in time, correct for roll error and altitude error. In a real flying platform, it would be desirable to perform maneuvers in which the craft simultaneously changed roll angle and altitude, as for example, simultaneously rolling from zero degrees to twenty degrees about one axis and climbing from 100 feet altitude to 150 feet. Jackson's control method does not specify how such integrated maneuvers could be carried out.
Paul S. Moller, U.S. Pat. No. 4,795,111, Jan. 3, 1989, discloses a flying platform using ducted fan engines. The invention is concerned with ducted fan engines as the means of propulsion and does not address a means of insuring stability of the craft, let alone a control algorithm.
Moller's disclosure principally addresses the specifications of the mechanical and aerodynamic problems associated with using ducted fan engines as a means of propulsion and attitude control. It is the regulation of thrust values in precise amounts which is the essence of the control problem, and Moller's disclosure does not address the specifics of how thrust values would be computed for a craft using such engines.
Lorant Forizs, U.S. Pat. No. 4,537,372, Aug. 27, 1985, discloses a two-thrustered craft which seems inherently unstable in that it would rotate freely about its long axis with no means of compensation of control.
As with the Moller disclosure, the Forizs disclosure gives no convincing description of how the craft would be stabilized in flight. Regardless of this, the lack of physical means for forcing rotation about the long axis renders the craft uncontrollable.
Cordova Maxwell Brady, U.S. Pat. No. 3,985,320, Oct. 12, 1976, relies on gyroscopic stabilizing forces for control.
As for the other disclosures mentioned, no specifics are given concerning how rotation forces would be scheduled to effect control of rotation about the craft's spatial axes.